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Proteins from organisms living in extreme conditions are of particular interest because of their potential for being templates for redesign of enzymes both in biotechnological and other industries. The crystal struc-ture of a proteinase K-like enzyme from a psychrotroph Serratiaspecies has been solved to 1.8 A˚ . | ềFEBS Journal The 1.8 A crystal structure of a proteinase K-like enzyme from a psychrotroph Serratia species Ronny Helland1 Atle Noralf Larsen2 Arne Oskar Smalas1 3 and Nils Peder Willassen1 2 1 Norwegian StructuralBiology Centre Faculty of Science University of Tromso Tromso Norway 2 Department of Molecular Biotechnology Faculty of Medicine University of Tromso Tromso Norway 3 Department of Chemistry Faculty of Science University of Tromso Tromso Norway Keywords proteinase K psychrophilic S binding substrate specificity subtilase subtilisin Correspondence R. Helland Norwegian StructuralBiology Centre Faculty of Science University of Tromso 9037 Tromso Norway Fax 47 77644765 Tel 47 77646474 E-mail ronny.helland@chem.uit.no Website http norstruct.uit.no Enzymes Serratia sp. peptidase EC 3.4.21.- proteinase K EC 3.4.21.64 Vibrio sp. peptidase EC 3.4.21.- . Received 7 September 2005 revised 25 October 2005 accepted 31 October 2005 doi 10.1111 j.1742-4658.2005.05040.x Proteins from organisms living in extreme conditions are of particular interest because of their potential for being templates for redesign of enzymes both in biotechnological and other industries. The crystal structure of a proteinase K-like enzyme from a psychrotroph Serratia species has been solved to 1.8 A. The structure has been compared with the structures of proteinase K from Tritirachium album Limber and Vibrio sp. PA44 in order to reveal structural explanations for differences in biophysical properties. The Serratia peptidase shares around 40 and 64 identity with the Tritirachium and Vibrio peptidases respectively. The fold of the three enzymes is essentially identical with minor exceptions in surface loops. One calcium binding site is found in the Serratia peptidase in contrast to the Tritirachium and Vibrio peptidases which have two and three respectively. A disulfide bridge close to the S2 site in the Serratia and Vibrio peptidases an extensive hydrogen bond network in a tight loop close to .
